Personal communication service (PCS) is a service in which subscribers, rather than locations or telephone stations, are assigned a personal telephone number. Calls placed to a subscriber's personal telephone number are routed to the subscriber at a telephone near that subscriber's current location. In order to provide a subscriber with such a personal communication service, e.g., as disclosed in U.S. Pat. No. 4,313,035, issued to Jordan, et al., the system providing the service (PCS system) must be supplied with the telephone number of a telephone near the subscriber's current location to which it should route calls placed to his personal telephone number. Each time the subscriber changes his location, the telephone number to which calls placed to his personal telephone number are routed must be changed. This requires the subscriber to call into the PCS system and to supply the telephone number to which his calls should currently be routed. Constantly having to call in to the PCS system can be tiresome, and supplying a ten-digit telephone number each time a subscriber changes his location is cumbersome.
To overcome these drawbacks, one prior art solution is to program a sequence of telephone numbers at any one of which the personal telephone service subscriber might be reached. The telephone numbers in a sequence are typically those of locations where a person is likely to be at various times thought the day, such as "home", "car phone", "office", "pager", etc. When a call is made to the subscriber's personal telephone number, the PCS system attempts to complete the call by sequentially routing the call to each telephone number in the sequence. Each attempt to complete the call to a telephone number of the sequence continues until a) the call is answered, b) the call is abandoned, c) the line associated with the telephone number is determined to be busy or d) until a predetermined period of time has elapsed.
Occasionally, a caller may place a call to the subscriber's personal telephone number from a telephone whose number is part of the sequence to be tried for the subscriber's personal telephone number. This situation might occur when a wife, calling from home, dials her husband's personal telephone number, which is programmed to attempt to reach him first at his office, then at home on the same telephone line on which his wife is calling, and finally, at his mobile telephone in his car. Assuming the husband has left work and is in his car, and further assuming that nobody answers the call at the office, an attempt will be made to route call to the home telephone on which the wife is calling before it is routed to the mobile telephone in the car. Attempting to route a PCS call back to the calling telephone wastes system resources by consuming unnecessary processing time, and may result in an unnecessary expense to the carrier of the PCS call if an access charge is incurred.
For such a call, the call flow is also affected if the calling telephone line is provisioned with the well known call waiting feature. This is because, at the point in the sequence that the PCS system attempts to complete the call to the telephone number of the calling telephone, the call waiting feature is activated by the caller's own call to the personal telephone number, thereby causing the caller to hear the call waiting tone. Such a call waiting tone is actually erroneous, since there is no actual other call, i.e., no call other than the call being placed by the caller himself, that is attempted to be completed to the calling telephone. Thus, if the home telephone in the above-described example is provisioned with call waiting, the wife will hear the erroneous call waiting tone. The erroneous call waiting tone will persist until the wife attempts to answer the apparent second call or until the predetermined time for attempting to complete the call to the home telephone number expires.
Such an erroneous call waiting tone is problematic. Firstly, the caller is put to an unnecessary choice, because he must choose whether to continue on the call he placed to the personal telephone number or whether to interrupt that call and answer what appears to him as a second call that is arriving at his telephone line. Since no actual second call is arriving at the caller's telephone line, but instead the there is only the illusion of a second call caused by the erroneous call waiting tone, there is actually no need for the caller to have to make such a choice. Secondly, the caller may become confused as a result of the erroneous call waiting tone because, if he answers the "illusory" second call represented to him by the call waiting tone, he will not actually answer a call but instead will be connected back to his own telephone line--which is on hold for call waiting purposes. Furthermore, should the caller then signal the call waiting feature to return him to his outgoing call, he will find that the PCS system is no longer attempting to connect his call to any further telephone numbers and, instead, has gone dead.